Flowing Floor Screed

Flowing screeds can have cement or calcium sulphate based binder agents. Calcium sulphate screed falls into the two catergories of Anhydrite / Alpha hemihydrite

As cement based systems continue to improve the calcium sulphate based systems may begin to falter.

Both systems allow for large areas to be completed over a short amount of time.  As the credit crunch begins to bite, some people are expecting anhydrite based systems to be pushed out of the market - due to fairly high costs and a lack of cheap housing to be available for application.

Advantages over traditional screed is that flowing screeds can finished quickly and they can be laid unbonded to an average of 40mm in commercial areas, with 35mm being acceptable in domestic environments. Disadvantages are that they tend to be more expensive, can be fairly unregular (SR2 ), have less crush resistance and suffer massively if regularly gets wet, and even worse flooded.  Flowing screeds cannot be worked to find falls in wet rooms and need extra preparation with respect to tiling the surface (This information is within the printed literature of the suppliers of these products, but are easily overlooked).

During the floods a few years ago in Sheffield, many liquid based screeds were entirely destroyed by the flooding. Rising waters got into buildings and caused screeds, laid using flowscreed, to be elevated by the insulation below and cause it to break.  This was compounded by the small amount of light-weight flowing screed that had been applied to large thicknesses of insulation required to get the flowing screed to the correct depth without the need for excessive amounts of flowing screed.

In comparison, there were traditional screeds (65mm) that had 4 feet of flood water over them, and witheld the force of the insulation below trying to float - even though these screeds were only ten days old.

I am not trying to undermine flowing screeds, it is important that people know what factors could ruin their floors, especially in areas with possible flood risk.